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At Nautilus: Under Anesthesia, Where Do Our Minds Go?


To better understand our brains and design safer anesthesia, scientists are turning to EEG.

Jackie Rocheleau writes:

After experimenting on a hen, his dog, his goldfish, and himself, dentist William Morton was ready. On Oct. 16, 1846, he hurried to the Massachusetts General Hospital surgical theater for what would be the first successful public test of a general anesthetic.

His concoction of sulfuric ether and oil from an orange (just for the fragrance) knocked a young man unconscious while a surgeon cut a tumor from his neck. To the onlooking students and clinicians, it was like a miracle. Some alchemical reaction between the ether and the man’s brain allowed him to slip into a state akin to light sleep, to undergo what should have been a painful surgery with little discomfort, and then to return to himself with only a hazy memory of the experience.

Monitoring patients’ brains still isn’t something that medical boards require.

General anesthesia redefined surgery and medicine, but over a century later it still carries significant risks. Too much sedation can lead to neurocognitive disorders and may even shorten lifespan; too little can lead to traumatic and painful wakefulness during surgery. So far, scientists have learned that, generally speaking, anesthetic drugs render people unconscious by altering how parts of the brain communicate. But they still don’t fully understand why. Although anesthesia works primarily on the brain, anesthesiologists do not regularly monitor the brain when they put patients under. And it is only in the past decade that neuroscientists interested in altered states of consciousness have begun taking advantage of anesthesia as a research tool. “It’s the central irony” of anesthesiology, says George Mashour, a University of Michigan neuroanesthesiologist, whose work entails keeping patients unconscious during neurosurgery and providing appropriate pain management.

Unlike the 1846 demonstration, when Morton merely administered the anesthetic and stepped aside for the surgeon, today anesthesiology entails maintenance: Clinicians are required to monitor the patient’s vital signs, like heart rate, blood pressure, and body temperature throughout the operation, adjusting dosages as needed. But monitoring patients’ brains still isn’t something that medical boards require or that medical schools train anesthesiologists to do in the operating room.


EEG records the electrochemical activity between communicating neurons in the brain. As the brain lapses into anesthetic-induced unconsciousness, this activity follows a predictable pattern of sequences. Through electrodes stuck to the scalp, EEG records these sequences, which are then visualized as spiky waves on a monitor. When a patient is under general anesthesia, typically the waves crest more slowly with greater amplitude as the drugs disrupt connections between networks that keep us awake and aware. For example, propofol enhances inhibition of cortical neurons and disrupts communication across the cortex, the hub of complex functions like thinking and making sense of stimuli from the environment. It also dampens communication between the cortex, the brainstem, and the thalamus, an egg-shaped collection of neurons deep within the brain important for sensory information processing and arousal.

In some of these states of unconsciousness, awareness of the self and the body remains intact.

Getting under the hood

A better understanding of how patients wake from anesthesia and under what circumstances they struggle could also help scientists with an even knottier problem: how to treat disorders of consciousness, including coma. General anesthesia lends itself to studying these questions, as researchers can control the transition into and out of unconsciousness and track how brain activity changes as the anesthetic takes hold and wears off. Like anesthesia, coma seems to alter essential communication between different brain networks. For example, in both coma and general anesthesia, communication between the cortex and thalamus slows.

General anesthesia is “a very good tool to disentangle responsiveness and unconsciousness because you can play on the verge of these two,” says Athena Demertzi, a research associate at the University of Liège in Belgium. “It’s especially fascinating to see how these brain network configurations change in different states of anesthesia.”

The complete article is available at Nautilus.

If artificial intelligence (AI) has anything to do with consciousness, what would be the equivalent of a general anesthesia for an AI machine?Where do our minds go” when we’re unconscious? The question itself implies that mind is more than machine.

Thanks for some helpful elaborations on mind/brain dualism. Caspian
There is no such thing as "Artificial Intelligence." People think AI is human level intelligence. It is not. It is just a series of computer programs. relatd
Using the perhaps over-simplistic TV set analogy for interactive dualism (which the empirical data from NDEs indicates is the correct theory of mind), in normal consciousness the spirit inhabits the physical body and especially the brain via a vast incredibly complicated interpenetration and intertwining with the neural structure. This is the ultimate causal interaction between mind and matter. With the TV set, the program information (pictures and sound) that is expressed or physically manifested by the picture tube and speakers is not generated in the TV set; with human consciousness it is not actually generated by the physical brain, but is an immaterial mobile center of consciousness inhabiting and interacting through the brain. The complicated circuitry of the TV set's function, rather than to actually generate the picture and sound programming, is to process the signals coming in from outside in order to physically express them as pictures and sound. In the human, the incredibly complex neural circuitry enables an interactive expression and physical manifestation of conscousness via the brain and body. So if in a contemporary Internet-ready TV the local Internet connection goes down, the TV set will no longer display the picture and sound of the programming. But the signals corresponding to this programming are not damaged or disrupted and are still being transmitted by the TV station and still exist on electronic media or live as camera feeds at the station. Another example: If the AC power going to the set is interrupted, or a lightning strike damages the internal circuitry of the set, the set will no longer display the programming. However, the intelligently originated program signals are not disrupted, just their processing in the TV set. Similarly, when consciousness in the patient is dampened by anesthetics, the expression of consciousness is also dampened because the incredibly complex circuitry of the brain is being temporarily disrupted. But the person's spirit is ultimately not damaged. If it seems damaged after general anesthesia, it must be because some of the neural circuitry is lastingly damaged. In the case of AI systems, the analogy doesn't hold. Whatever cleverly programmed impersonation or imitation of conscious intelligence is being displayed and communicated by the AI is in fact being generated by the AI, and therefore is in truth being turned off or damaged by the outside forces. However, since consciousness and qualia are non-calculatable and non-algorithmic, and all computers of any level of advancement can do is to calculate using algorithms, computers no matter how highly advanced can never even in principle generate the qualia of subjective consciousness and awareness (courtesy Robert J. Marks). doubter

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